This application proposes to conduct a Stage 1 treatment development study targeting a subtype of drug abusing adolescent, those with Borderline Personality Disorder (BPD), that has proved to be particularly difficult to treat. The proposed intervention, Borderline Adolescent Family Therapy (BAFT) integrates two successful traditions in intervention research: Structural Family Therapy for drug abusing adolescents with individual skills building components derived from the work of Marsha Linehan with Borderlines. The proposed study is divided into two phases. Phase I is the BAFT development phase including: developing a "working" BAFT manual integrating individual and family components based on archived videotapes, conducting BAFT with three cases to determine ways of enhancing feasibility and acceptability of the modality, and enhancing the focus of BAFT interventions on mechanisms of change specific to families of BPD drug abusing adolescents; and developing a refined BAFT manual, a manual for therapist selection and training, and a measure of adherence. Phase II consists of a randomized pilot study of 24 cases using a control condition comprised of referrals to community agencies. Analyses are intended to provide information for determining effect sizes for the analyses that will be required in a Stage II efficacy trial, viz., MANOVAs on outcomes (drug abuse, borderline behaviors, conduct problems, and markers of individuals skills development); MANOVAs on postulated mechanisms of actions (family patterns of interactions, negativity/positivity, and therapeutic alliances). Moreover, analyses of clinical significance will be used to identify subgroups for whom the intervention works best, and growth curve analyses will be used to compare the course of change in mechanisms of action between successful and unsuccessful cases.